import java.util.HashSet;
import java.util.Scanner;

public class HJ10 {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        String s = sc.nextLine();
        System.out.println(getDiffNum(s));
    }

    public static int getDiffNum(String s){
        HashSet set = new HashSet();
        char[] ch = s.toCharArray();
        for(char c:ch){
            set.add(c);
        }
        return set.size();
    }
}
